A friendship provided the seed that blossomed into a composition.

On a September day in 1988, two old friends--both longtime members of the Peninsula Symphony board--got together for a chat. But it wasn’t just the usual friendly visit.

Patrick Rossetti, a civil engineer whose career had ranged from World War II defense work to private construction, had an idea for a musical suite celebrating California.

It would begin with a cataclysmic earthquake that created the land and go on to depict California’s progression from a land of native Indians and Spanish colonizers to a modern state with a vast population and freeways.

During their visit, Rossetti asked Conrad Wedberg--a USC administrator who had started composing music in college--to take his saga and set it to music. Rossetti had been impressed by arrangements Wedberg had made for the orchestra, notably a Cole Porter medley.

“He said write what you want, how you want it,” recalled Wedberg, who proceeded to do just that. During the nearly two years it took to compose the piece, Wedberg kept his collaborator posted on his musical ideas.

For his part, Rossetti once said his major contribution to the music was “simple observations like ‘Write this symphony or I may not speak to you again.’ ”

Rossetti had sponsored vocal and instrumental ensembles in the past, and he persuaded the Peninsula Symphony to do Wedberg’s suite. The work that the two friends produced--”Queen of the Angels Suite”--will receive its world premiere Saturday during a free concert by the Peninsula Symphony. The concert, at the Rolling Hills Covenant Auditorium, also includes works by Rimsky-Korsakov, Alexis Emmanuel Chabrier and Shostakovich.

Conductor Joseph A. Valenti said the 22-minute Wedberg-Rossetti piece should please the audience. “It’s euphonic, and there is not so much distortion. It has some very creative points,” he said.

A high point, Valenti said, is an earthquake, depicted through “acceleration, tremors and rumbles in the music,” that joins the ancient island of California to the mainland.

The premiere is an unusual event for the 24-year-old community orchestra, which will assemble 80 musicians for the concert. The orchestra rarely plays original compositions, and the suite is the first piece ever dedicated to it.

Although Saturday promises to be a gala evening for Wedberg--who will discuss his work before the concert--there will also be sadness because of Rossetti’s absence. He died of cancer March 21 without ever hearing the composition in full.

However, Rossetti got to hear some of the piece, thanks to the computer hooked to a synthesizer that Wedberg uses when he composes. “I saw him a week before he died,” recalled Wedberg, who received the computer as a retirement gift last June. “I took a tape I’d made on my machine. He was able to hear a few portions, and he was quite pleased.”

Rossetti, whose comments about the music are included in the symphony program book, was “a very altruistic, genial human being,” Wedberg said. He added that Rossetti probably would be the first to tell Saturday’s audience, “Don’t grieve, have fun.”

A confirmed patron of the RTD for trips between his Rancho Palos Verdes home and USC, Wedberg said he came up with 90% of his musical ideas for the suite on the two hours a day he spent on the bus.

And friends on the bus sometimes helped him out of musical jams. Said Wedberg, “There were two ladies (who one day) asked me how it was going, and I said I was having a heck of a time with the fourth movement. They said, ‘Why not adapt a theme from a previous movement?’ ”

When his wife, Elizabeth, picked him up at the bus stop that night, she asked him how the piece was going. He mentioned his dilemma, and she also said he should use a former theme. “The suggestion fell in place, and I wrote it on the bus the next day going to work,” he said.

Wedberg said his biggest musical challenge was presenting themes that have been done before--native Indians and Spanish colonizers--in new and different ways.

“Popular Indian music is tom-toms,” he said. “I didn’t want to do that. I got the same effect through pizzicato strings.” Depicting a Spanish maiden longing for Spain in the hostile New World also was a struggle. “I decided to use a flute solo,” Wedberg said. “It would be somewhat wistful, and the flute player loved it.”

Until his retirement from USC as associate director of governmental affairs, Wedberg spent 43 years at the university. He had little time to write music during those years, but it was always “in the back of my mind,” he said.

With the university behind him, he hopes the suite will be the first of several compositions to bear his name. “I’d like to write one-act comic operas and operettas,” he said.

Right now, Wedberg is happy with the attention his suite is getting: “I feel very privileged. I think of the thousands of composers who never hear their music. I’ve been blessed with a performance, and I think it’s just incredible.”

What: The Peninsula Symphony.

When: Saturday, 8:30 p.m.

Where: Rolling Hills Covenant Auditorium, 2222 Palos Verdes Drive North, Rolling Hills Estates.

Admission: Free.

Information: 544-0320.